Method of producing a packaging material

ABSTRACT

A method of producing a packaging laminate ( 10 ) in which a web is provided with through-going holes ( 2 ) which are covered on one side with a first outer layer ( 3 ) on the one side of the web and with a second outer layer ( 4 ) on the other side of the web in such a manner that the first and second outer layers ( 3  and  4 ) are permanently sealed to one another within the regions of the opening contour of the through-going holes. In order to ensure the permanent seal between the two outer layers ( 3  and  4 ), the web is subjected, after application of the first outer layer but prior to application of the second outer layer, to so-called flame-treating whereby accessible parts of the first outer layer within the regions of the through-going holes ( 2 ) are activated or polarized by means of one or more gas flames directed at the other side of the web.

FIELD OF THE INVENTION

The present invention relates to a method of producing a packagingmaterial comprising a core layer with through-going holes which arecovered by a first layer applied on one side of the core layer, and asecond layer applied on the other side of the core layer, the first andsecond layers being bonded to one another within the regions of theopening contour of the through-going holes, the method comprising thesteps of providing a web of core layer with through-going holes, coatingthe one side of the web with a first layer, and thereafter coating theother side of the web with a second layer in such a manner that thefirst and second layers are sealed to one another within the regions ofthe opening contour of the through-going holes.

BACKGROUND OF THE INVENTION

Packaging containers of the single use disposable type for liquid foodsare often produced from a packaging material of the type mentionedabove. Once such commonly occurring packaging container is that which ismarketed under the trademark Tetra Brik® and which is principallyemployed for liquid foods such as milk, fruit juice etc. The packagingmaterial in this known packaging container typically comprises a corelayer of paper or paperboard and outer, liquid-tight layers ofthermoplastic.

In order to render the packaging container light- and gas-tight, inparticular oxygen gas-tight, as well, the material in these packagingcontainers is normally supplemented with at least one additional layer,often an aluminium foil (Alifoi]) which moreover renders the packagingmaterial thermosealable by inductive thermosealing which is a rapid andefficient sealing technique for obtaining mechanically strong, liquid-and gas-tight sealing joints or scams during the production of thecontainers.

Packaging containers are nowadays most generally produced by means ofmodem packing machines of the type which form, fill and seal packagesfrom a web or from prefabricated blanks of packaging material.

From, for example, a web, packaging containers are produced in that theweb is reformed into a tube by both of the longitudinal edges of the webbeing united to one another in an overlap joint. The tube is filled withthe intended relevant contents and is divided into individual packagesby repeated transverse seals of the tube a distance from one anotherbelow the level of the contents in the tube. The packages are separatedfrom the tube by incisions in the transverse seals and are given thedesired geometric configuration, normally parallelepipedie, by foldformation along prepared crease lines in the packaging material.

From consumer quarters, it is desirable that the packaging container beeasy to handle and easy to open when it is time to empty the package ofits contents, and in order to satisfy this need, the packaging containeris often provided with some type of opening arrangement, with the aid ofwhich it may readily be opened without the need to employ scissors orother implements.

A commonly occurring opening arrangement in such packaging containersincludes a hole punched in the core layer of the package wall, the holebeing covered, on the inside and outside of the package wall, by therespective outer layers of the packaging wall which are sealed to oneanother in the region of the opening contour of the through-going hole.Moreover, the prior art opening arrangement generally has a separatepull-tab or opening strip which is applied over the hole and which isrupturably sealed to the outer layer of the outside of the package wallalong a sealing joint around the entire opening contour of the hole andat the same time permanently sealed to the outer layer in the regioninside the opening contour of the hole.

When the packaging container is to be opened and emptied of itscontents, the pull-tab or opening strip is pulled off, the rupturableseal between the pull-tab and the outer layer being ruptured at the sametime as the two outer layers are torn off along the opening contour ofthe hole and accompany adhering to the pull-tab for exposure of thethrough-going hole through which the contents of the packaging containermay thereafter readily be poured.

One precondition for this opening arrangement to function efficientlyand expediently and expose all of the pouring hole is thus that thepermanent seal between the pull-tab and the outer layer on the outsideof the packaging wall is sufficiently strong so as not to be rupturedwhen the pull-tab is pulled off, and further the seal between the twoouter layers must, within the region of the opening contour of the hole,also be sufficiently strong to ensure that both of the layers are pulledoff adhering to one another.

Both of these preconditions are, as a rule, easy to satisfy withpackaging containers in which both of the respective outer layers of thepackaging material consist exclusively of simple, easily sealedthermoplastic layers, while, on the other hand, it is not an uncommonoccurrence that problems arise in packaging containers in which one orboth of the outer layers of the packaging material also include a layerof another material than thermoplastic, such as, for example, analuminum foil which is often employed in packaging containers for oxygengas-sensitive products, such as juice, etc.

When the outer layer on the inside of the packaging wall also includesan aluminium foil which, by the intermediary of a sealing- or laminationlayer, is connected to the outer layer on the inside of the packagingwall within the region of the opening contour of the hole, itoccasionally happens that the seal between the two outer layers of thepackaging wall is unintentionally ruptured when the opening strip orpull-tab is pulled off, and that the outer layer on the inside of thepackaging wall at best is only partly removed from the hole. As aresult, the remaining part of the outer layer will prevent or impedepouring out of the contents of the packaging container.

SUMMARY OF THE INVENTION

One object of the present invention is therefore to obviate theabove-described problem in connection with the prior art packagingcontainers.

A further object of the present invention is to realise a simple, butefficient method of producing a packaging material for a packagingcontainer with a well-functioning opening arrangement of the typedescribed above.

One particular object of the present invention is to realise a method ofproducing a packaging material for a packaging container with an openingarrangement of the type described above which ensures an efficient andexpedient opening function of the packaging container also in that casewhen the container wall includes an aluminium foil in at least one ofits two outer layers.

These and other objects and advantages will be attained according to thepresent invention in that the method disclosed by way of introductionhas been given the characterising features as described herein.

Advantageous and expedient embodiments of the method according to the Apresent invention have further been given the characterising features asdescribed herein.

According to the present invention, there will thus be realised a methodof producing a packaging material comprising a core layer withthrough-going holes which are covered by a first outer layer applied onone side of the core layer and a second outer layer applied on the otherside of the core layer, both the first and second outer layers beingsealed to one another in the region inside the opening contour of thehole, the method comprising the steps of providing a web of core layerwith through-going holes by punching, coating one side of the web with afirst outer layer, and thereafter coating the other side of the web witha second outer layer in such a manner that the two first and secondouter layers are sealed to one another in the region inside the openingcontour of the through-going holes, the method being characterised inthat the holed web, after coating with the first outer layer but priorto coating with the second outer layer, is subjected to treatment byso-called flame-treating in that the web is caused to pass at least onegas flame directed at the second, or uncoated, side of the web and bymeans of which accessible parts of the first outer layer are, for thepurpose of promoting adhesion, activated or polarised in the regioninside the opening contour of the through-going holes.

As a result of the above-disclosed surface treatment by means ofso-called flame-treating, a polarisation or activation will be achievedof the bonding sites on the parts of the first outer layer accessiblefrom the second, or uncoated, side, the polarised or activated bondingsites ensuring a permanent seal between the first and second outerlayers when the second outer layer, in a subsequent coating operation,is applied to the web.

In one preferred embodiment of the method according to the presentinvention, the web consists of a web of paper or paperboard which isunwound from a magazine reel and which, after punching of thethrough-going holes, is coated on its one side with a first outer layerof thermoplastic, preferably polyethylene, which is extruded as acontinuous curtain or film against one side of the web. The web with theextruded, first thermoplastic layer is thereafter subjected to a surfacetreatment by so-called flame-treating in that the web is caused to passone or more gas flames directed at the uncoated or second side of theweb and by means of which the accessible parts of the firstthermoplastic layer are polarised or surface activated in the regioninside the opening contour of the through-going holes. The web isthereafter coated with a second outer layer of thermoplastic, preferablypolyethylene, which is extruded as a continuous curtain or film againstthe second side of the web and is permanently sealed to the polarised oractivated parts of the first thermoplastic layer, in the region insidethe through-going holes.

In another embodiment of the method according to the present invention,a laminated packaging material for a packaging container for oxygengas-sensitive liquid products such as juice, etc., is produced, thepackaging material having a core layer of paper or paperboard, a firstouter layer of thermoplastic, preferably LDPE (low densitypolyethylene), applied on one side of the core layer and a second outerlayer applied on the other side of the web and including an aluminiumfoil serving as light- and oxygen gas-barrier, and an outermost layer ofthermoplastic, preferably LDPE, this second outer layer being sealed tothe core layer by the intermediary of a sealing- or lamination layer,preferably LDPE. A web of paper or paperboard of suitable packagingquality is unwound from a magazine reel and provided with through-goingholes by punching. The one side of the web is coated with a with afirst, continuous outer layer of thermoplastic, preferably LDPE, byextrusion, and is thereafter caused to pass one or more gas flamesdirected at the second or uncoated side of the web and by means of whichthe accessible parts of the first, outer layer are, for the purpose ofpromoting adhesion, polarised or activated in the region inside thethrough-going holes. The web is thereafter coated with a second layer ofaluminium foil and extruded layer of thermoplastic, preferably LDPE, thesecond layer being bonded to the web by the intermediary of a sealing-or lamination layer which is extruded between the web and the second,outer layer in such a manner that it is permanently sealed to thepolarised or activated first, outer layer in the region inside theopening contour of the through-going holes.

In order further to improve the sealing bond between the first layer ofthermoplastic and the paper or paperboard web, the first thermoplasticlayer is extruded preferably during the supply or, or in an atmosphereof ozone, which activates and/or generates bonding seats or sites in thesurface of the thermoplastic layer so that the thermoplastic layer issealed to the one side of the web with high sealing strength.

In order to amplify the scaling strength between, on the one hand, theweb and the sealing- or lamination layer and, on the other hand, betweenthe sealing- or lamination layer and the aluminium foil of the secondouter layer, the sealing- or lamination layer is preferably alsoextruded during the supply of, or in an atmosphere of ozone whichactivates and/or generates the bonding seats or sites in the surface ofthe sealing- or lamination layer so that this layer, with good sealingstrength, can be sealed to both the web and to the aluminium foil.

As has already been mentioned, the second outer layer in this embodimenthas an outermost layer of thermoplastic, preferably LDPE, bonded to thealuminium foil, and, in order to ensure a good bonding seal between thealuminium foil and the outermost thermoplastic layer, it is preferredaccording to the present invention to subject the exposed surface of thealuminium foil (facing away from the sealing- or lamination layer) to asealing-promoting surface treatment prior to contact with the extrudedoutermost thermoplastic layer. Such a sealing-promoting treatment of thealuminium foil may, according to the present invention, suitably be putinto effect using so-called flame-treating or corona-treating.

In an alternative embodiment of the method according to the presentinvention, a laminated packaging material with the same laminatestructure as that described above, i.e. a laminate structure in which atleast one of the two outer layers also includes an aluminium foil, maybe produced in that a web of paper or paperboard of suitable packagingquality is unwound from a magazine reel and provided with through-goingholes by punching, as previously. The holed web is thereafter coated onits one side with a first outer layer which, in this embodiment,includes an outermost layer of thermoplastic, preferably LDPE, and analuminium foil. The aluminium foil is sealed to the web by theintermediary of a sealing- or lamination layer which is extruded betweenthe web and the aluminium foil at the same time as the other surface ofthe aluminium foil (facing away from the web) is coated with theabove-mentioned outermost layer of thermoplastic by extrusion.

The web with the thus applied first, outer layer is thereafter caused topass one or more gas flames directed at the second, or uncoated side ofthe web and by means of which accessible parts of the surface of theextruded sealing- or lamination layer in the region inside the openingcontour of the through-going holes is, for the purpose of promotingadhesion, polarised or activated in order to increase the ability of thescaling- or lamination layer to bond to another outer thermoplasticlayer, preferably LDPE, which, in a subsequent coating operation, isextruded in a continuous layer against the second, or uncoated side ofthe web.

As in the earlier embodiment, the sealing strength between both the weband the extruded sealing- or lamination layer and between the sealing-or lamination layer and the aluminium foil can also be improved if thesealing- or lamination layer is extruded under the supply of, or in thepresence of an atmosphere of ozone which activates and/or generatesactive bonding seats in the extruded surface of the sealing- orlamination layer so that this layer is sealed and bonded to the web andthe aluminium foil, respectively, with high sealing strength.

A superior bonding or integrity of the two layers in the first outerlayer, i.e. the aluminium foil and the outermost thermoplastic layer, isensured in that the exposed surface of the aluminium foil (facing awayfrom the web) is, prior to contact with the extruded, outermostthermoplastic layer, polarised or activated for the purpose of promotingadhesion by a suitable treatment which, according to the presentinvention, may be put into effect by means of so-called flame-treatingor by corona-treating.

The web with the applied first layer which is surface activated for thepurpose of promoting adhesion is thereafter bonded to a second layer ofthermoplastic, preferably LDPE, which is extruded against the second, oruncoated, side of the web. Preferably, the second layer is extrudedunder the supply of, or in an atmosphere of ozone which activates and/orgenerates active bonding seats on the surface of the second layer bymeans of which this layer is permanently sealed to the web.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in greater detailhereinbelow with particular reference to the accompanying Drawings, inwhich:

FIG. 1 is a schematic cross sectional view of a packaging material ofconventional type for oxygen gas-sensitive products producing by themethod according to the present invention;

FIG. 2 schematically illustrates how the packaging material of FIG. 1may be produced by the method according to a first embodiment of thepresent invention; and

FIG. 3 schematically illustrates how the packaging material of FIG. 1may be produced by the method according to a second embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically illustrates a cross section of a packaging laminatefor a packaging container for oxygen gas-sensitive products such asjuice, etc.

The packaging laminate, carrying the generic reference numeral 10, has acore layer 1 of paper or paperboard of conventional packaging quality,with through-going holes 2 which, on the one, or upper side of the corelayer 1, are coated by a first, outer layer 3 of thermoplastic,preferably LDPE, and on the second, or lower side of the core layer 1,by a second outer layer 4 which, in the illustrated example, includes analuminium foil 4 a serving as light- and oxygen gas-barrier, and anoutermost or lowermost layer 4 b of thermoplastic, preferably LDPE. Thesecond layer 4 is bonded to both the core layer 1 and to the first layer3 in the region inside the through-going hole 2 by a sealing- orlamination layer 5 applied between the core layer 1 and the first layer3, respectively.

As shown in FIG. 1, the packaging laminate 10 also has a pull- oropening tab 6 applied on the first outer layer 3 and with a free end 6 aserving as pull- or gripping tab with the aid of which the tab 6 isintended to be removed by pulling off for exposure of the hole 2.

In order to make possible such an exposure of the hole 2, the strip 6 ispermanently sealed to the first outer layer 3 in the region inside theopening contour of the hole 2. Further, the two outer layers 3 and 4must also be sealed to one another by the intermediary of theinterjacent sealing- or lamination layer 5 with such sealing strengththat the sealing joint between these two outer layers is not broken bythe action of the tractive force which is applied on the opening stripor tab 6 when this is pulled off. A further requirement for ensuring acomplete exposure of the hole 2 when the opening strip or pull tab 6 ispulled off is that the internal sealing strength between the two layers4 a and 4 b must also be sufficiently strong to prevent the second outerlayer 4 from delaminating.

The illustrated packaging laminate 10 in FIG. 1 can, according to thepresent invention, be produced in the manner which is schematicallyillustrated in FIG. 2 and which effectively ensures that all conditionsand preconditions for the intended opening function of the pull tab oropening strip 6 be satisfied.

From a magazine 1′ to the left in the Figure, a web 1 of paper orpaperboard of suitable packaging quality is unwound. The unwound web 1is led, in the direction of the illustrated arrow, to a first processingstation at 7 where the web, in a conventional method and usingpreviously known means, is provided with through-going holes 2 (FIG. 1)by a punching operation. Since neither the method nor the equipment forproviding the web 1 with these holes constitutes any germane part of thepresent invention, they will not be described in greater detail in thiscontext.

The holed web 1 is thereafter led further to a first coating station at8 where the web is led through the nip between two rollers 8 a and 8 brotating in the direction of transport of the web, at the same time asthe one side of the web 1 is coated with a first outer layer 3 (FIG. 1)which, by means of an extruder 8 c, is extruded in the form of acontinuous film 3 against the web 1 when this is led in and through thenip between the rollers 8 a and 8 b.

From the coating station 8, the web 1 is led with the applied firstouter layer 3 further to a treatment station at 9 where the web 1 is, bymeans of number (two in the illustrated example) of gas flames 9 a and 9b directed at the second, or uncoated, side of the web 1, subjected toan activation or polarisation treatment during which accessible parts ofthe first outer layer 3 are activated or polarised by the action of theabove-mentioned gas flames 9 a and 9 b within the regions of the openingcontour of the through-going holes.

From the treatment station 9, the thus treated web 1 is led via abending roller 10 to a second coating station at 11 wherein the web 1,on its second, or uncoated, side, is coated with a sealing- orlamination layer 5 which is extruded against the web 1 by means of anextruder 11 a. The web 1 with the extruded sealing- or lamination layer5 is united with a web 4 a of aluminum foil unrolled from a magazinereel 4 a′ and is led through the nip between two rollers 11 b and 11 crotating in the direction of transport of the web, whereby the aluminiumfoil 4 a is, by the intermediary of the extruded sealing- or laminationlayer 5, sealed with good bonding adhesion permanently to both the web 1and to the available, activated or polarised parts of the first outerlayer 3 in the regions inside the opening contours of the through-goingholes. In connection, with or after the passage though nip between thetwo rollers 11 b and 11 c, the exposed side (facing away from the web 1)of the aluminium foil 4 a is coated with an outermost layer 4 b ofthermoplastic which is extruded in a continuous layer from an extruder11 d and sealed to the foil-coated web 1 for obtaining a web-shapedpackaging material 10 substantially possessing the layer composition asshown in FIG. 1.

The web-shaped packaging material 10 is thereafter supplemented withseparate pull or opening strips or tabs 6 (FIG. 1) which, either inconnection with the production of the packaging material or at a lateroccasion, for example when the packaging material 10 is reformed intopackaging containers, are applied on the outer layer 3 of the packagingmaterial 10 along a rupturable sealing joint around the opening contourof the through-going holes, at the same time as the pull tabs or openingstrips 6 are sealed permanently to the outer layer 3 in the regioninside the opening contour of the through-going holes in order therebyto ensure the expedient opening function of the opening strips or pulltabs, as described above.

The packaging material 10 in FIG. 1 may, in alternative embodiment ofthe method according to the present invention, also be produced in themanner which is schematically illustrated in FIG. 3. For identical orsimilar parts as in FIGS. 1 and 2, the same reference numerals have beenemployed in FIG. 3.

From a magazine 1′ in the upper, left-hand part of FIG. 3, a web 1 ofpaper or paperboard of suitable packaging quality is unwound. Theunwound web 1 is led, in the direction of the illustrated arrow, to afirst processing station at 7 where the web, in a conventional methodand using previously known means, is provided with through-going holes 2(FIG. 1) by a punching operation. Since neither the method nor theequipment for providing the web 1 with through-going holes neither inthis embodiment constitutes any germane part of the present invention,they will not be described in greater detail in this context.

The holed web 1 is thereafter led further to a first coating station at8 where one side of the web 1 is combined with a web 4 a of aluminiumfoil unwound from a magazine reel 4 a′ at the same time as a sealing- orlamination layer 5 is extruded between the web 1 and the aluminium foil4 a by means of an extruder 8 c, in the region of the entry of the web 1into the nip between two rollers 8 a and 8 b rotating in the directionof transport of the web 1.

The exposed side (facing away from the web 1) of the aluminium foil 4 ais coated with an outermost layer 4 b of thermoplastic which is extrudedin a continuous layer by means of an extruder lid and is sealedpermanently to the foil-coated web 1 when this is led through the nipbetween two rollers 12 a and 12 b rotating in the direction of transportof the web 1 in association with the extruder lid.

After exit from the nip between the rollers 12 a and 12 b, the web 1 isled with the applied outer layer 4 (FIG. 1) via a bending roller 10 to aprocessing station at 9 where the web 1 is, by means of number (two inthe illustrated example) of gas flames 9 a and 9 b directed at thesecond, or uncoated, side of the web 1, subjected to an activation orpolarisation treatment during which accessible parts of the outer layer4 are activated or polarised by the action of the above-mentioned gasflames 9 a and 9 b within the regions of the opening contour of thethrough-going holes.

The thus activated or polarized web 1 for purposes of promoting adhesionis thereafter led further to a second coating station at 11 where theweb 1 is led through the nip between two rollers 11 b and 11 c rotatingin the direction of transport of the web, at the same time as theuncoated side of the web 1 is coated with an outer layer 3 (FIG. 1)which, by means of an extruder 11 a, is extruded in the form of acontinuous layer against the web 1 when this is led in and through thenip between the rollers 11 b and 11 c. The layer 3 will, in thisinstance, be permanently sealed to the above-mentioned activated orpolarised parts of the outer layer 4 within the region of the openingcontour of the through-going holes, for obtaining a web-shaped packagingmaterial 10 substantially having the layer composition as shown in FIG.1.

The web-shaped packaging material 10 is thereafter supplemented withseparate pull or opening strips or tabs 6 (FIG. 1) which, either inconnection with the production of the packaging material or at a lateroccasion, for example when the packaging material 10 is reformed intopackaging containers, are applied on the outer layer 3 of the packagingmaterial 10 along a rupturable sealing joint around the opening contourof the through-going holes, at the same time as the pull tabs or openingstrips 6 are sealed permanently to the outer layer 3 in the regioninside the opening contour of the through-going holes in order therebyto ensure a well-operating opening function for the opening strips orpull tabs, as described above.

1. A method of producing a packaging laminate for a packaging containercomprising a wall and an emptying opening including a through-holepenetrating the wall, the through-hole being covered on the outside ofthe container by a first outer layer of thermoplastic and on the insideof the container by a second outer layer comprising aluminum foil and alayer of thermoplastic, the first outer layer and second outer layerbeing releasably sealed to each other within the region of the openingcontour of the through-hole by a pull or opening strip on the outside ofthe wall, the method comprising: providing a web of paper or paperboardwith through-holes; covering the through-holes on a first side of theweb with a first outer layer of a thermoplastic; and then covering thethrough-holes on a second side of the web with a second outer layercomprising aluminum foil and a layer of thermoplastic such that thefirst outer layer and second outer layer are sealed to each other withinthe regions of the opening contours of the through-holes by a sealing-or lamination layer extruded between the first outer layer and secondouter layer.
 2. The method as claimed in claim 1, wherein the secondouter layer is applied with the aluminum foil facing towards and incontact with the sealing- or lamination layer; and the sealing- orlamination layer is, to promote adhesion, extruded in an atmosphere ofozone.
 3. The method as claimed in claim 2, wherein: the surface of thealuminum foil facing away from the sealing- or lamination layer issubjected to an activation or polarization treatment by flame-treatingor by corona-treating, whereby the aluminum foil is, to promoteadhesion, activated or polarized; and the as-treated surface of thealuminum foil is coated with an outermost layer which, through activatedor polarized bonding seats of the aluminum foil, is permanently sealedto the aluminum foil.
 4. The method as claimed in claim 1, wherein boththe first outer layer and layer of thermoplastic of the second outerlayer consist of low density polyethylene.
 5. A method of producing apackaging laminate comprising a core layer with through-going holeswhich are covered by a first outer layer applied on a first side of thecore layer, and a second outer layer applied on a second side of thecore layer, the first and second outer layers being sealed to oneanother within the regions of the through-going holes, the methodcomprising: providing a web of a core layer with through-going holes,coating the second side of the web with a second outer layer includingan aluminum foil facing towards the web and an outermost layer appliedon the surface of the aluminum foil facing away from the web, andthereafter coating the first side of the web with a first outer layersuch a that the first and second outer layers are sealed to one anotherwithin the regions of the opening contour of the through-going holes andthe aluminum foil and the outermost layer are disposed within theregions of the through-going holes: wherein the web with thethrough-going holes, after coating with the second outer layer but priorto coating with the first outer layer, is subjected to flame-treatingduring which the web is caused to pass one or more gas flames directedat the first side of the web and accessible parts of the second outerlayer are, to promote adhesion, activated or polarized within theregions of the through-going holes.
 6. The method as claimed in claim 5,wherein the first outer layer and second outer layer are sealed to oneanother by the intermediary of a sealing- or lamination layer which isextruded between the first outer layer and second outer layer.
 7. Themethod as claimed in claim 6, wherein the sealing- or lamination layeris to promote adhesion, extruded in an atmosphere of ozone.
 8. Themethod as claimed in claim 6, wherein: the surface of the aluminum foilfacing away from the sealing- or lamination layer is subjected to anactivation or polarization treatment by flame-treating or bycorona-treating, whereby the aluminum foil is, to promote adhesion,activated or polarized; and as-activated or polarized surface of thealuminum foil is coated with the outermost layer which, through theactivated or polarized bonding seats of the aluminum foil, ispermanently sealed to the aluminum foil.
 9. The method as claimed inclaim 5, wherein the core layer consists of paper or paperboard; andboth the first outer layer and the outermost layer of the second layerconsist of thermoplastic.
 10. The method as claimed in claim 1, whereinthe packaging laminate comprises separate opening strips or pull tabswhich are applied on the first outer layer of the packaging laminatesuch that the opening strips or pull tabs are sealed to the first outerlayer in a rupturable sealing joint around the opening contour of eachrespective through-going hole, at the same time that the opening stripsor pull tabs are sealed permanently to the first outer layer within theregions of each respective opening contour of the through-going holes.11. A packaging container which is produced from a packaging laminateproduced according to the method as claimed in claim
 1. 12. The methodas claimed in claim 1, wherein the surface of the aluminum foil facingaway from the sealing- or lamination layer is subjected to an activationor polarization treatment by flame-treating or by corona-treating,whereby the aluminum foil is, to promote adhesion, activated orpolarized, and the as-treated surface of the aluminum foil is coatedwith an outermost layer which, through the activated or polarizedbonding seats of the aluminum foil, is permanently sealed to thealuminum foil.
 13. A packaging container which is produced from apackaging laminate produced according to the method as claimed in claim5.
 14. The method as claimed in claim 5, wherein the core layer consistsof paper or paperboard; and both the first outer layer and the outermostlayer of the second layer consist of low density polyethylene.